Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Remove the wires and tubes from the air pressure switch (noting their locations)
Connect the APS testing kit and FGA to the APS (P1 / +ve connection)
Connect the APS testing kit and FGA to the APS (P1 / +ve connection)
Measurement:
Steadily increase the pressure using the syringe to that shown on the APS.
(pressure may be shown on rear of APS, remove / loosen securing screw to view)
Measure the resistance between the common (3) and normally open (2) terminals.
Continuity / zero resistance should be measured.
Notes:
1. If continuity is not obtained it is permissible to increase the pressure by 50%.
2. 100 Pascals = 1mb / 50 Pascals = 0.5mb.
3. Terminals are numbered on the air pressure switch.
(pressure may be shown on rear of APS, remove / loosen securing screw to view)
Measure the resistance between the common (3) and normally open (2) terminals.
Continuity / zero resistance should be measured.
Notes:
1. If continuity is not obtained it is permissible to increase the pressure by 50%.
2. 100 Pascals = 1mb / 50 Pascals = 0.5mb.
3. Terminals are numbered on the air pressure switch.
Isolate as per TOPs P4
and refit as necessary